package com.xiaoge.basedevlibrary.utils;

/**
 * Created with IntelliJ IDEA.
 * User: nachebang
 * Date: 14-11-6
 * Time: 下午5:46
 * To change this template use File | Settings | File Templates.
 */

import java.security.MessageDigest;

public class MD5 {

    private MD5() {

    }

    /**十六进制下数字到字符的映射数组  */
    private final static String[] hexDigits = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

        /**  对字符串进行MD5加密     */
    public static String md5(String originString){
        if (originString != null){
             try{
                  //创建具有指定算法名称的信息摘要
                  MessageDigest md = MessageDigest.getInstance("MD5");
                  //使用指定的字节数组对摘要进行最后更新，然后完成摘要计算
                  byte[] results = md.digest(originString.getBytes());
                  //将得到的字节数组变成字符串返回
                  String resultString = byteArrayToHexString(results);
                  return resultString.toUpperCase();
             } catch(Exception ex){
                  ex.printStackTrace();
             }
        }
            return null;
    }

        /**
         * 转换字节数组为十六进制字符串
         * @param     字节数组
         * @return    十六进制字符串
         */
    private static String byteArrayToHexString(byte[] b){
        StringBuffer resultSb = new StringBuffer();
        for (int i = 0; i < b.length; i++){
           resultSb.append(byteToHexString(b[i]));
        }
        return resultSb.toString();
    }

    /** 将一个字节转化成十六进制形式的字符串     */
    private static String byteToHexString(byte b){
        int n = b;
        if (n < 0) {
           n = 256 + n;
        }
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

}
